A critical component of worker safety for fumigators monitoring phosphine gas levels is an accurate monitoring device. Researchers evaluated accuracy levels of four electronic devices and a tube-type device while monitoring Oklahoma grain elevators under fumigation; particular attention was paid to accuracy levels in the dangerous range. Average accuracy of the electronic devices ranged from 60% to 100%. Although the tube-type device was technically the most accurate, in practice it may be less accurate due to operator error in reading the tubes. It is important for safety educators to fully understand the benefits and limitations of phosphine monitoring devices.